“Were it feasible, it would make sense to measure all income and expense in real terms since capital gains, like all forms of capital income, partly represent inflation. But indexing only capital gains make no sense. It could cut capital gains taxes by up to $20 billion a year—nearly all for the richest Americans—and open the door to a raft of new, inefficient tax shelters.”

Tax Policy Center

The right generally supports indexing capital gains to inflation, provided it is done by Congress.

Some dispute the analyses suggesting that this would primarily benefit the wealthy: “No model can estimate how much revenue might be lost by indexing

if any

because that depends on such unknowable things as future asset values, future tax laws and future inflation...